这是单元测试的工作示例：

index.tsx：

import React from 'react';

const styles = {
  sendEmail: 'sendEmail'
};

export const SendProjectManagerEmail = ({ sendEmail }) => {
  return (
    <button id="send-project-manager-email-button" className={styles.sendEmail} onClick={() => sendEmail()}>
      Resend Email
    </button>
  );
};

index.spec.tsx：

import { SendProjectManagerEmail } from './';
import { mount } from 'enzyme';
import React from 'react';

describe('SendProjectManagerEmail',() => {
  it('renders disabled button',() => {
    const mockFn = jest.fn();
    const wrapper = mount(<SendProjectManagerEmail sendEmail={mockFn} />);
    const button = wrapper.find('#send-project-manager-email-button');
    button.simulate('click');
    expect(mockFn).toHaveBeenCalledTimes(1);
  });
});

覆盖率100％的单元测试结果：

 PASS  src/stackoverflow/58808783/index.spec.tsx
  SendProjectManagerEmail
    ✓ renders disabled button (201ms)

-----------|----------|----------|----------|----------|-------------------|
File       |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------|----------|----------|----------|----------|-------------------|
All files  |      100 |      100 |      100 |      100 |                   |
 index.tsx |      100 |      100 |      100 |      100 |                   |
-----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed,1 total
Tests:       1 passed,1 total
Snapshots:   0 total
Time:        4.604s,estimated 10s

源代码：https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/58808783